Longitudinal transformation of nitrogen and carbon in the hyporheic zone of an N-rich stream: A combined modelling and field study

A combined modelling and field study approach was used to examine biogeochemical functioning of the hyporheic zone in two gravel bars in an N-rich fourth-order stream (River Hers, south-west France). Surfacewater and interstitial water were sampledmonthly (August 1994–January 1995), the latter in a network of 29 piezometers in the first gravel bar and 17 in the second. In both gravel bars, the hyporheic zone was created only by advected channelwater without any connectionwith groundwater. Longitudinal chemical profiles of Dissolved Organic Carbon (DOC), nitrate (NO3–N), ammonium (NH4–N) and Dissolved Oxygen (DO) were established for both gravel bars. Ambient and potential denitrification weremeasured in the laboratory during the same period using the acetylene inhibition technique. Factors limiting denitrification were also examined by testing the separate effects of nitrate or nitrate + carbon additions. A 1D reactive-transport model was used to simulate longitudinal transformation of nitrogen in the hyporheic zone, and to estimate the role of organic matter (DOC and POC) in the biogeochemical functioning of the hyporheic zone. Denitrification measurements with nitrate and nitrate + carbon additions both showed increased denitrification, suggesting that denitrification might not be C-limited at this site. Observations and model results showed the hyporheic zone to be a sink of DOC and nitrate, but DOC consumption appeared insufficient to explain nitrate depletion measured in the two gravel bars. Field data were better modelled when an additional DOC source from the POC fraction degraded by anaerobic respiration was included in the model

Contribution à la conception de coupleurs magnétiques robustes pour convertisseurs multicellulaires parallèles

Face aux enjeux énergétiques actuels, l’électronique de puissance est un domaine de recherche de premier plan. La relative fragilité des composants présents dans les chaines de conversion implique néanmoins de devoir prendre en compte la gestion des défaillances dès la phase de conception. La défaillance d'un composant est une situation hautement critique tant sur le plan de la sécurité environnante que sur le plan de l'indisponibilité du système qui en découle. Cette problématique de sureté de fonctionnement constitue la ligne directive de ce travail de thèse, visant à imaginer, et concevoir des solutions permettant de sécuriser ces structures en présence de défauts. Dans cette thèse, nous étudions de nouveaux composants magnétiques offrant un excellent compromis entre la densité de puissance traitée et rendement de conversion, mais très sensibles à toutes perturbations électriques. Une méthode de pré-dimensionnement des composants magnétiques a été développée et des solutions ont été apportés pour sécuriser et maintenir le fonctionnement du la chaine de conversion suite à l’apparition de plusieurs défauts. ABSTRACT : In the research field, power electronics is an important issue in the actual energy challenges. Nowadays, new converters, called « multilevel or multicell converters », are used in many applications requiring high-current with high-power density. This is due to their high frequency performances and good waveforms signals. The main advantages of such converters concern the high efficiency and good system integration. Most embedded systems are required to maintain operation even if failures or faults occur. New magnetic devices called InterCell Transformers (ICTs) in multicell converters help to improve the efficiency and compactness. Nevertheless, such magnetic components are inherently sensitive to any impecfection coming from the converter. The goal of this PhD thesis is to bring solutions to make ICTs more fault tolerant. Therefore, a pre-design methodology for a robust ICT is presented in order to maintain the operation after the occurrence of one or several faults. Several solutions are presented and detaille

Nucleolar localization of influenza A NS1: striking differences between mammalian and avian cells

In mammalian cells, nucleolar localization of influenza A NS1 requires the presence of a C-terminal nucleolar localization signal. This nucleolar localization signal is present only in certain strains of influenza A viruses. Therefore, only certain NS1 accumulate in the nucleolus of mammalian cells. In contrast, we show that all NS1 tested in this study accumulated in the nucleolus of avian cells even in the absence of the above described C-terminal nucleolar localization signal. Thus, nucleolar localization of NS1 in avian cells appears to rely on a different nucleolar localization signal that is more conserved among influenza virus strains

Régime alimentaire du grand gecko vert de Madagascar, Phelsuma grandis Gray, 1870 sur l'île de La Réunion (Squamata : Gekkonidae)

RÉSUMÉ : Phelsuma grandis Gray, 1870 est un gecko introduit sur l’île de La Réunion. Le régime alimentaire de ce reptile, considéré comme invasif, a été étudié afin d’évaluer la menace qu'il pourrait représenter pour la faune indigène. Le contenu stomacal de 171 individus a été analysé. À La Réunion, P. grandis se nourrit principalement d’Arthropodes. Les ressources végétales occupent également une part non négligeable de son alimentation et il consomme régulièrement d’autres espèces de geckos. P. grandis manifeste un comportement alimentaire de type opportuniste, à large spectre de proies. Ces résultats indiquent que P. grandis pourrait avoir des incidences négatives importantes sur la faune locale, notamment sur l’entomofaune et l’herpétofaune par prédation ou par compétition.ABSTRACT:Phelsuma grandis Gray, 1870 is an introduced invasive gecko at Reunion Island. The aim of the present study was to assess its diet in order to evaluate the threat it could represent for native fauna. Stomach contents of 171 individuals were analyzed. At Reunion Island, P. grandis feeds mostly on arthropods and, to a lesser extent, plant materials. P. grandis feeds also, and regularly, onother gecko species. P. grandis shows an opportunistic feeding behavior with a broad spectrum of prey. These outcomes indicate that P. grandis may have significant negative impacts on the local wildlife, including entomofauna and herpetofauna, through predation or competition.MOTS CLÉS : Phelsuma grandis, espèce invasive, prédation, écosystèmes insulaires.KEYWORDS : Phelsuma grandis, invasive species, predation, island ecosystems

Toward a Play Management System for Play-Based Learning

International audienceThis position paper is dedicated to describing a preliminary model of an integrated system, called Play Management System (PMS). PMS is designed to support both players and teachers to deliver, use, manage and track play situations. This PMS model results from a design-based research methodology. Our approach focuses on (1) the learners and the situation that emerges when they play the game, rather than the system dedicated to play and (2) the teachers who want to manage a game-based learning situation. Thus, we argue for a shift from a game-based to a play-based perspective. 1 Introduction Within a context marked by the development of alternative pedagogies, this position paper aims to describe a model of an integrated system, called Play Management System (PMS), dedicated to support players and teachers to deliver, use, manage and track play situations. The purpose of this article is to propose an innovative approach for implementing a play-based learning approach by (1) focusing on the learners and taking into consideration the situation that emerges when they play rather than the artifact dedicated to play (play vs game) and (2) focusing on the teachers who want to implement and manage a play-based learning situation in their classroom (play management vs game design). Thus, we address the issue of teachers' requirements for the orchestration of a play situation within an educational context. In the first section of this paper, we advocate for a player-centered approach for game-based learning. The second section presents a game developed during the project and the design-based research methodology adopted for designing this game. The third section describe

Well-defined hyperstar copolymers based on a thiol–yne hyperbranched core and a poly(2-oxazoline) shell for biomedical applications

Well defined ‘hyperstar’ copolymers were synthesized by combining hyperbranched polymers produced by thiol–yne chemistry with poly(oxazoline)s. The hyperbranched core was prepared using an AB2 monomer and a trifunctional alkene, applying a monomer feeding approach. The degree of branching was high (0.9) while maintaining low dispersities (1.3). Poly(2-ethyl-2-oxazoline) (PEtOx) functionalized with a thiol end group was coupled to the surface of the hyperbranched structure accessing terminal alkyne units. PEtOx-SH was produced by the termination of the living polymerization with ethyl xanthate and subsequent conversion to thiol under alkaline conditions. The degree of polymerization was varied producing PEtOx with 23 or 42 repeating units, respectively with a dispersity of around 1.1. After conjugation of the polymer arms, hyperstar copolymers were characterized by SEC, NMR spectroscopy, light scattering, and AFM. The polymers were able to encapsulate the hydrophobic dye Nile red within the core of the structure with loading efficiencies between 0.3 and 0.9 wt%. Cytotoxicity of the hyperstars was assessed using A2780 human ovarian carcinoma cells resulting in IC50 values of around 0.7 mg ml−1. Successful internalization and colocalization with lysosomal compartments was observed by confocal microscopy studies

Tribbles expression in cumulus cells is related to oocyte maturation and fatty acid metabolism.

International audienceIn mammals, the Tribbles family includes widely expressed serine-threonine kinase-like proteins (TRIB1, TRIB2 and TRIB3) that are involved in multiple biological processes including cell proliferation and fatty acid (FA) metabolism. Our recent studies highlighted the importance of FA metabolism in cumulus cells (CC) during oocyte maturation in vertebrates and reported a higher TRIB1 expression in CC surrounding in vivo mature oocytes as compared to immature ooocytes in mice and cows. The objective was to investigate Tribbles expression patterns in bovine CC during in vitro maturation (IVM) and to examine their roles in the cumulus-oocyte complex